Dinâmicas de uso e ocupação do solo e transformação ambiental da Microrregião de Porto Nacional/MATOPIBA, Tocantins - Brasil

Abstract

This thesis investigated, through a multiscale analytical framework, the effects of agricultural expansion on plinthic soils in the microregion of Porto Nacional, located within MATOPIBA—one of Brazil’s leading agricultural frontiers. The overarching objective was to evaluate how land use and land cover, geomorphological conditions, and the physical–hydraulic and mineralogical properties of a PLINTOSSOLO PÉTRICO Concrecionary influence environmental dynamics and susceptibility to erosion, integrating spatial, temporal, and field-based experimental analyses. The methodological structure encompassed three analytical levels. At the regional scale (Chapter 2), geospatial landscape analysis, morphodynamic modeling, and the assessment of spatiotemporal land-use and land-cover change from 1985 to 2022 were conducted, including predictive modeling validated for projections up to 2055. Geotechnologies—GIS, 30-m DEMs, satellite imagery, and derived environmental metrics—enabled the identification of transformation patterns and critical areas under agro-environmental pressure. At the intermediate scale (Chapter 3), the focus was on territorial reorganization, the expansion of monocultures and pasturelands, and the intensification of agricultural use, highlighting the replacement of native vegetation by high-impact crops, especially soybean. At the local and experimental scale (Chapter 4), morphological, mineralogical (XRD), elemental (XRF), and physical–hydraulic properties of the PLINTOSSOLO PÉTRICO Concrecionary were characterized, alongside the application of the Revised Universal Soil Loss Equation (RUSLE) at the regional scale to estimate soil loss and evaluate laminar erosion vulnerability according to land-use patterns in the Porto Nacional/MATOPIBA microregion. Integrated results from the land-use/land-cover modeling revealed an accelerated replacement of savanna and forest formations by agricultural crops and pasturelands, with soybean cultivation showing continuous expansion since the 1990s and a strong tendency toward further growth in the coming decades. At the local scale, the PLINTOSSOLO PÉTRICO Concrecionary exhibited marked sensitivity to mechanization, manifested by reductions in hydrodynamic functionality and increased erosion susceptibility, especially on steeper slopes. This behavior results from a set of edaphic and mineralogical attributes, including the high proportion of micropores (59.5%), clayey texture (43.1%), and elevated contents of gibbsite and kaolinite, which promote the formation of rigid and compacted structures. These conditions contribute to the development of plinthite and ferruginous concretions, reducing infiltration and increasing surface runoff. The seasonal tropical climate, combined with no-tillage systems (SPD) on terrain with 3–8% slopes, further intensifies these processes. The RUSLE results indicated that the microregion is largely characterized by very low to moderate soil-loss rates (0.01–2.0 t·ha−1·yr−1), consistent with areas under native vegetation or conservation-oriented management. However, localized hotspots reached values of approximately 7 t·ha−1·yr−1 in areas dominated by conventional agriculture and degraded pastures. The spatial distribution of erosion demonstrated a strong control exerted by relief and land use, evidencing that the conversion of native environments into intensive agricultural systems significantly alters the stability of the pedological system. In Chapter 5, the integration of multiscale findings revealed that regional landscape dynamics, productive reorganization, and the intrinsic properties of the PLINTOSSOLO PÉTRICO Concrecionary converge to create a scenario of increasing environmental vulnerability, particularly under conditions of agricultural intensification. The articulation among chapters showed that land-use changes directly affect soil hydrodynamics and erosion susceptibility, reinforcing the need for conservation practices and environmental planning. Overall, this thesis provides essential scientific and technical contributions for territorial planning, soil conservation, and environmental management in the MATOPIBA region. It highlights the importance of integrated approaches linking relief, soil, and land use, as well as the central role of geotechnologies as diagnostic tools and support mechanisms for decision-making.